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Research Papers: Design and Analysis

Fitness-for-Service Evaluation of Thermal Hot Spots and Corrosion Damage in Cylindrical Pressure Components

[+] Author and Article Information
P. Tantichattanont, S. M. R. Adluri

Faculty of Engineering and Applied Science, Memorial University, St. John’s. NL, A1B 3X5, Canada

Faculty of Engineering and Applied Science, Memorial University, St. John’s. NL, A1B 3X5, Canadasesh@engr.mun.ca

J. Pressure Vessel Technol 131(5), 051206 (Sep 03, 2009) (10 pages) doi:10.1115/1.3148088 History: Received November 25, 2008; Revised November 26, 2008; Published September 03, 2009

Abstract

Thermal hot spots and corrosion damage are typical of damages occurring in pressure vessels and piping. Structural integrity of such components needs to be evaluated periodically to determine “fitness-for-service” (FFS) of the components. In the present paper, three alternative methods for level 2 FFS assessments (as described in API 579) are proposed. They are based on variational principles in plasticity, the $m$-alpha method, the idea of reference volume, and the concept of decay lengths in shells. Decay lengths in the axial and circumferential directions for cylindrical shells are derived based on elastic shell theories. They are used to specify the reference volume participating in plastic action and the extent of what can be called “local” damage. Interaction between longitudinal and circumferential effects is investigated. A linear interaction curve is shown to give good estimation of the “remaining strength factor” for damage of practical aspect ratios. The stretching and bulging effects due to the damage are also studied. The limit defining the threshold to dominance of stretching action is proposed by using an approximate equilibrium calculation based on yield-line analysis. The effectiveness of the proposed assessments is demonstrated through an example and verified by level 3 inelastic finite element analysis.

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Figures

Figure 1

Thin cylindrical shell

Figure 2

Linear and elliptic interaction curves

Figure 3

Extent for local damage for different values of slope parameter α

Figure 4

Yield line mechanism of an approximate rectangular flat plate

Figure 5

Reference dimensions for localized effect in cylindrical shell

Figure 6

RSF recommendations for various sizes of damaged areas: (a) RSFr-1, (b) RSFr-2, (c) RSFr-3

Figure 7

Idealized bulging geometry

Figure 8

Comparison of RSFr and RSFi for cylindrical shells

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